1. Field of the Invention
The present invention relates to an adjustable dumbbell, and more particularly to an adjustable dumbbell assembly having an easily and quickly adjustable structure.
2. Description of the Prior Art
Various kinds of typical adjustable dumbbells have been developed. U.S. Pat. No. 4,566,690 to Schook, and U.S. Pat. No. 5,407,413 to Kupferman disclose two of the typical dumbbells each including one or more weight rings that may be selectively or adjustably secured together for adjusting the weight of the dumbbells.
In U.S. Pat. No. 4,566,690 to Schook, the weight rings each includes an outer thread for threading with the inner threads of the other weight rings and for securing the weight rings together. It takes time to thread the weight rings together.
In U.S. Pat. No. 5,407,413 to Kupferman, the weight rings are engaged on a core or a rod and each includes a number of posts for engaging into the holes of the other weight rings. It is also required to secure the weight rings together one by one. In addition, the weight rings may be rotated and disengaged from each other while in use.
U.S. Pat. No. 5,839,997 to Roth et al. discloses another typical adjustable dumbbell including a number of weight rings to be selectively or adjustably secured together with a shaft that is required to be rotated relative to the weight rings or the like. However, the weight rings or weight members may not be solidly secured to the shaft while in use.
The present invention has arisen to mitigate and/or obviate the afore-described disadvantages of the conventional adjustable dumbbells.